Differentiated Instructions; Coding Right-Hand Instructions - Omron SYSMAC C2000H Operation Manual

Coding Right-hand Instructions

5-4

Differentiated Instructions

00000
00000
5-5

Coding Right-hand Instructions

104
Most instructions are provided in both differentiated and non-differentiated
forms. Differentiated instructions are distinguished by an @ in front of the
instruction mnemonic.
A non-differentiated instruction is executed each time it is scanned as long as
its execution condition is ON. A differentiated instruction is executed only
once after its execution condition goes from OFF to ON. If the execution con-
dition has not changed or has changed from ON to OFF since the last time
the instruction was scanned, the instruction will not be executed. The follow-
ing two examples show how this works with MOV(21) and @MOV(21), which
are used to move the data in the address designated by the first operand to
the address designated by the second operand.
Diagram A
Diagram B
In diagram A, the non-differentiated MOV(21) will move the content of HR 10
to DM 0000 whenever it is scanned with 00000. If the cycle time is 80 ms and
00000 remains ON for 2.0 seconds, this move operation will be performed 25
times and only the last value moved to DM 0000 will be preserved there.
In diagram B, the differentiated @MOV(21) will move the content of HR 10 to
DM 0000 only once after 00000 goes ON. Even if 00000 remains ON for 2.0
seconds with the same 80 ms cycle time, the move operation will be exe-
cuted only during the first cycle in which 00000 has changed from OFF to
ON. Because the content of HR 10 could very well change during the 2 sec-
onds while 00000 is ON, the final content of DM 0000 after the 2 seconds
could be different depending on whether MOV(21) or @MOV(21) was used.
All operands, ladder diagram symbols, and other specifications for instruc-
tions are the same regardless of whether the differentiated or non-differen-
tiated form of an instruction is used. When inputting, the same function codes
are also used, but NOT is input after the function code to designate the differ-
entiated form of an instruction. Most, but not all, instructions have differenti-
ated forms.
Refer to 5-7 INTERLOCK and INTERLOCK CLEAR – IL(02) and IL(03) for
the effects of interlocks on differentiated instructions.
The C1000H and C2000H also provide differentiation instructions: DIFU(13)
and DIFD(14). DIFU(13) operates the same as a differentiated instruction,
but is used to turn ON a bit for one cycle. DIFD(14) also turns ON a bit for
one cycle, but does it when the execution condition has changed from ON to
OFF. Refer to 5-6-2 DIFFERENTIATE UP and DIFFERENTIATE DOWN –
DIFU(13) and DIFD(14) for details.
Writing mnemonic code for ladder instructions is described in Section 4 Writ-
ing and Inputting the Program. Converting the information in the ladder dia-
Address Instruction
MOV(21)
HR 10 00000
00001
DM 0000
@MOV(21)
Address Instruction
HR 10
00000
DM 0000
00001
Section 5-5
Operands
LD 00000
MOV(21)
HR
DM 0000
Operands
LD 00000
@MOV(21)
HR
DM 0000
10
10